This study will compare the sensitivity of the 1 mcg ACTH stimulation test to gold standard insulin tolerance testing in determining hypothalamic- pituitary-adrenal recovery in patients status post surgery for Cushing's syndrome secondary to pituitary or adrenal adenomas. These two tests will also be compared in patients with suspected hypopituitarism, to determine the ACTH test's sensitivity in screening for dysfunction. If the ACTH test has sufficient sensitivity, it could replace the insulin test in clinical practice.